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 Posted: Sat Jul 12, 2008 6:19 am |
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Guest
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It seems there is an error in this Wikipedia article:
http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction
Faraday's law says the induced EMF is in proportion to the rate of CHANGE
(my emphasis) of the magnetic flux. The article describes this much OK.
Later on, the article then says:
In the case of motional EMF, the idea is to move all or part of the
circuit through the magnetic field, for example, as in a homopolar
generator.
But this last case is a situation where the magnetic flux does not change.
Isn't this the aspect that Faraday saw as a paradox because it did not obey
his law of induction? Apparently he realized that no flux change happened
when he rotated the magnets with the rotating disk in his unipolar generator.
As I understand all this, there are TWO ways to induce electricity from a
magnetic field:
1. A conductor at a right angle to the magnetic field alignment experiencing
a change in the magnetic field flux density (strength). [Faraday's law
of induction]
2. Motion of a conductor at right angle to the magnetic field alignment and
simultaneously at right angle to the line of the conductor. [Fleming's
right hand rule, Lorentz force law]
The article seems to be trying to convert everything into one.
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| Benj... |
| Posted: Sat Jul 12, 2008 6:19 am |
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Guest
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On Jul 12, 7:19 am, phil-news-nos... at (no spam) ipal.net wrote:
Quote: As I understand all this, there are TWO ways to induce electricity from a
magnetic field:
1. A conductor at a right angle to the magnetic field alignment experiencing
a change in the magnetic field flux density (strength). [Faraday's law
of induction]
2. Motion of a conductor at right angle to the magnetic field alignment and
simultaneously at right angle to the line of the conductor. [Fleming's
right hand rule, Lorentz force law]
The article seems to be trying to convert everything into one.
Not really. Yes there are two ways and electric field can be produced
in a conductor (wire). One would be the relative motion between a
magnetic field and the conductor. That is related to the Lorentz force
law on charges. A simple example would be the moving of a magnet in
and out of a coil of wire. Also generators work on this principle and
the calculation of operation this way is usually called "flux cutting"
methods. The wires pass through the flux "cutting" it and producing
Lorentz EMF inside the wires.
The other way of producing electric fields inside wires is known as
"flux changing". IF we have two coils of wire and we put a current
through one of them, a pulse of voltage appears in the other. Note
that NOTHING is moving so there is no "flux cutting". Only the flux
through the second coil is changing because the current in the first
coil is changing.
So now there are TWO ways to produce an "emf" in a wire by means of
magnetic flux. But flux methods of BOTH types are limited. Sometimes
they fail altogether! A Faraday generator is a perfect example. The
magnetic field is not changing so there is no flux changing. And since
the disk is solid and continuous it really isn't "cutting" the flux
either. There are other examples of geometry that show the failure of
flux methods. Feynman notes that in such cases you go back to first
principles (Maxwell's equations) no matter how handy flux methods are
in calculating answers in many practical cases. In the case of mutual
induction the Vector Magnetic Potential can be seen to play a vital
role.
There have been many attempts to convert these two things into one.
For example people have argued that as a current increases in a wire
the magnetic field expands from the wire and thus produces Lorentz
forces in neighboring wires. These theories to date have all failed.
Flux theories have all pretty much failed to be fundamental. In fact
the whole concept of "lines of flux" is rather bogus to begin with!
Not that they are not useful, mind you.
So yes, there is no combining these things. You are allowed to go
"fix" the Wikipedia article you know! |
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| Posted: Sat Jul 12, 2008 11:22 am |
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Guest
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On Sat, 12 Jul 2008 06:30:50 -0700 (PDT) Benj <bjacoby at (no spam) iwaynet.net> wrote:
| On Jul 12, 7:19 am, phil-news-nos... at (no spam) ipal.net wrote:
|
|> As I understand all this, there are TWO ways to induce electricity from a
|> magnetic field:
|>
|> 1. A conductor at a right angle to the magnetic field alignment experiencing
|> a change in the magnetic field flux density (strength). [Faraday's law
|> of induction]
|>
|> 2. Motion of a conductor at right angle to the magnetic field alignment and
|> simultaneously at right angle to the line of the conductor. [Fleming's
|> right hand rule, Lorentz force law]
|>
|> The article seems to be trying to convert everything into one.
|
| Not really. Yes there are two ways and electric field can be produced
| in a conductor (wire). One would be the relative motion between a
| magnetic field and the conductor. That is related to the Lorentz force
| law on charges. A simple example would be the moving of a magnet in
| and out of a coil of wire. Also generators work on this principle and
| the calculation of operation this way is usually called "flux cutting"
| methods. The wires pass through the flux "cutting" it and producing
| Lorentz EMF inside the wires.
|
| The other way of producing electric fields inside wires is known as
| "flux changing". IF we have two coils of wire and we put a current
| through one of them, a pulse of voltage appears in the other. Note
| that NOTHING is moving so there is no "flux cutting". Only the flux
| through the second coil is changing because the current in the first
| coil is changing.
|
| So now there are TWO ways to produce an "emf" in a wire by means of
| magnetic flux. But flux methods of BOTH types are limited. Sometimes
| they fail altogether! A Faraday generator is a perfect example. The
| magnetic field is not changing so there is no flux changing. And since
| the disk is solid and continuous it really isn't "cutting" the flux
| either. There are other examples of geometry that show the failure of
| flux methods. Feynman notes that in such cases you go back to first
| principles (Maxwell's equations) no matter how handy flux methods are
| in calculating answers in many practical cases. In the case of mutual
| induction the Vector Magnetic Potential can be seen to play a vital
| role.
I don't see an issue with considering the Faraday generator solid disk as not
fitting the Lorentz force law. "Cutting" was an erroneous convenience that
explained some things prior to understanding this in terms of particles.
Certainly there are cases where you have to consider both laws to figure out
what is happening. But how does a transformer need the Lorentz law? How does
the Faraday disk need Maxwell's upgrade of Faraday's law?
| There have been many attempts to convert these two things into one.
| For example people have argued that as a current increases in a wire
| the magnetic field expands from the wire and thus produces Lorentz
| forces in neighboring wires. These theories to date have all failed.
| Flux theories have all pretty much failed to be fundamental. In fact
| the whole concept of "lines of flux" is rather bogus to begin with!
| Not that they are not useful, mind you.
If you want to convert both laws into one, you will have to consider space
and time as a single entity, and use a vector product that works between them.
| So yes, there is no combining these things. You are allowed to go
| "fix" the Wikipedia article you know!
This is an area I still have a lot to learn about. Unfortunately, many of the
puzzles I am pondering are not addressed in the multitudes of examples I have
found both in Wikipedia and elsewhere. Google has helped, but it doesn't seen
to have a way to do a search like "take the example described on this page and
find a page that describes a scenario which transposes the field and the motion
and flips the EMF".
For example, instead of using a solid disk in the Faraday generator, use a
spoked wheel. I did see one such example somewhere online with the claim
that it works the same as the solid disk, but only described a scenario of
stationary magnets creating a uniform field over the entire wheel. Now
change this to rotate the magnets with the wheel. I don't see why it would
be any different than the disk with rotating magnets, but I cannot be 100%
sure since apparently no one tested it (so I might have to). However, I am
more interested in additional modification of this wheel with a non-uniform
magnetic field, using magnets rotating with the wheel. So it still should
be a case of no flux change for any particle of the wheel mass itself. What
would be different is that some spokes have the field in one direction and
other spokes have the field in the other direction. So I would expect the
latter spokes to be producing an EMF in the opposite direction, continuously.
If I need to do a test of this, it would seem the best way to measure current
between alternating spokes would be to have some kind of low voltage light on
the wheel itself. That way, there are no external wire leads that could be
influenced by the flux changing going on in the extraneous field that reaches
beyond the wheel. I would expect this extraneous field to be much less since
the field lines would be between the opposing magnets instead of being limited
to being between the opposite sides of the wheel assembly. I expect this to
better confine the field to the wheel. Still, what remains of the extraneous
field could disturb the experiment.
I also suggest that instead of having what amounts to a group of loops making
up the wheel (a loop exists between each spoke pair with opposite fields), the
alternating spokes could be "wired in series" by breaking the loop near the
edge for loops in one direction, and near the axis for loops in the other
direction. This would end up being a zig-zag around the wheel, where even
spokes doing the zig have a field in one direction, and odd spokes doing the
zag have a field on the other direction. Shouldn't this series circuit have
an increased voltage with less current?
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| Benj... |
| Posted: Sat Jul 12, 2008 12:03 pm |
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On Jul 12, 12:22 pm, phil-news-nos... at (no spam) ipal.net wrote:
I'll say this much. I'm also very much interested in this subject and
would like to try to find a way to combine Lorentz and Faraday laws
into one thing. I DO believe that as you put a current down a wire the
magnetic field expands aways from a wire causing an apparent Lorentz
force at a distance. After all, we know that as we put current down a
wire energy is stored in the magnetic field. Causality means that
energy is traveling away from the wire at the speed of light or
slower. Therefore, the "expanding field" theory could make sense. But
I've never found a calculation that would work to prove this. You try
and nothing ends up making sense.
Also as for Faraday Disks including the One Piece Faraday Homopolar
Device (OPFHD) which means magnets rotate with disk. You CAN split the
disk into radials or as Tesla proposed into a spiral which actually
enhances the magnetic field as it produces current. It works the same.
Yes then in the case of non-rotating magnets one actually can then say
that the wires DO "cut" the flux. But in the one piece case, the
problem is that you are using a loop to measure emf. One scenario is
this: The magnet and the disk turn together. Therefore, there is NO
emf induced into the disk no matter WHAT it's configuration! There is
NO relative motion between them. The emf you are measuring is coming
ALL from the wire loops hooked between the disk and meter. A similar
argument ensues if you assume the magnetic field does not rotate with
the magnet.
These kind of experiments are easy to do. I've done quite a few. Just
find some old dead large loudspeakers and remove the large ceramic
disk magnets from them (they are usually glued in so it can take some
work). Then set up your ideas. The voltages and currents from a
Faraday disk should easily light most LEDs. But dig. They DON'T! All
your various ideas somehow almost always seem to forget about the
"complete" loop thing. The laws of line integrals in a conservative
magnetic field are totally unforgiving! Nope, the LEDs do NOT light!
Just gets you scratching your head. Evenually I had to join everyone
else in the idea that the measurement cannot be made with a loop. It
has to be made electrostatically. I don't like it, but it's just how
it is. |
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| Benj... |
| Posted: Sat Jul 12, 2008 7:13 pm |
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Guest
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On Jul 12, 9:18 pm, phil-news-nos... at (no spam) ipal.net wrote:
Quote: That's an interesting one I had not seen. I looked at one patent Tesla
got that involved two disks edge to edge connected by some kind of belt
to make it easier to extract power. Back to Google.
Yes, the dual Faraday generator used flanged disks with a copper mesh
belt around them. This places (if you choose magnetic polarity
correctly) the two generators in series which doubles the voltage (I
think Tesla had the idea of a series of these to get voltages to
useful ranges) and also lets the brushes be on the disk shafts rather
than sliding on the disks (which has lots of friction and losses at
the low voltages and high currents).
The spiral one was interesting too in that he was trying build a "self-
excited" Faraday generator. The idea was that the high currents in the
spiral rotor automatically generate a stator field without a field
supply or permanent magnets.
Quote: Are you saying this in terms of an argument one may face and have to ponder
or are you saying that the OPFHD really produces no EMF at all?
The OPFHG actually produces voltage (which seems rather amazing at
first) But if you use Lorentz arguments you have to say that since
there is no relative motion between the magnet and disk there can be
no Lorentz voltage. Thus EITHER the field rotates with the magnet and
ALL the output voltage comes from the non-disk part of the circuit OR
the field does NOT rotate with magnet in which case the voltage comes
from the disk [no relative motion then between magnetic field and
external wiring].
Quote: There is the counter argument that if the magnets rotate, and the disk
does not (wires are attached to measure), then this should induce some
voltage in the attached wires as well. Yet this configuration nets no
EMF.
The actual counter argument actually involves the case with the disk
stationary and the brushes and meter are moving around the disk. And
that DOES produce a voltage.
Quote: If the OPFHD really produces no EMF at all, then there was no paradox?
But is does produce voltage. In fact the SAME voltage as if the
magnets didn't move.
Quote: I plan to buy some strong neodymium magnets to try things with when I do pick
an experiment to try.
Me too! But right now I"m using Speaker magnets. One experiment is to
encase the whole thing in an iron magnetic circuit (as Tesla did)
Iron elements complicate the picture but I'm wondering what the effect
of such flux concentration would be on output voltage and current.
Especially if you spin the disk, magnets AND iron circuit! The thing
I'm building needs a bit more machining before I try it.
Quote: I don't know what you mean by "measurement cannot be made with a loop". I am
not suggesting some kind of loop coupling to sense the EMF in the disk/wheel.
It means that if you are measuring output using a meter and a
"circuit" there is a loop of wire there and you MUST consider the
ENTIRE loop for Lorentz forces. Consider the following: A spinning
magnet. a "Loop" consisting of a wire down the axis of the disk shaft.
A wire vertically up the face of the magnet. A wire away from the
magnet following a "line of flux" and finally a vertical wire back
down to the shaft where it is twisted with the other wire and goes to
the meter. The standard thought is that if you make the flux line
wires long enough, the downward wire will be in such a weak field that
you can ignore any induction there. That is totally wrong!
Dig. The wire down the shaft follows a fluxline and has no induction.
The upper wire following a flux line has no induction. The twisted
wire pair has no induced voltages. The wire up the magnet face will
have the Lorentz force you expect due to the relative motion of the
magnetic field and the wire. So far the experiment has everyone fat
and happy. But wait. If you look closely, you'll find that the SAME
flux lines that cut the wire on the magnet face ALSO cut the DOWNWARD
connecting wire and do it in the OPPOSITE sense. You can show the
induced voltages are equal and opposite! Hence you can experiment
until you are blue in the face and you get NOTHING! And that also
includes no conclusions! So long as there is a loop in the field you
simply can't get around this cancellation! It turns out the loop shape
makes no difference. This is why people suggest using electrostatic
measurements which do NOT use a closed circuit to measure emf.
Quote: The loop is to generate a larger EMF potential. Putting the light on the
wheel itself is a means to directly measure without using brushes on the
disk.
Tried it. But if you think about it, you see that wires going to the
light are the part of the light-loop! No light is seen.
Quote: I'm also considering the drum configuration. The conductors would run along
the drum parallel to the axis. The field would be radial to/from the axis.
And of course the motion would be circular around the drum.
Yes the drum configuration is good, See the old EM books by E.G.
Cullwick who derives a lot on the drum and notes the "meter and
brushes" relative motion thing.
Good luck!
WARNING: Due to extreme spam, googlegroups.com is blocked.
Hey, I'm posting in GoogleGroups.com! How am I getting through? Is
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| Posted: Sat Jul 12, 2008 8:18 pm |
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Guest
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On Sat, 12 Jul 2008 15:03:02 -0700 (PDT) Benj <bjacoby at (no spam) iwaynet.net> wrote:
| I'll say this much. I'm also very much interested in this subject and
| would like to try to find a way to combine Lorentz and Faraday laws
| into one thing. I DO believe that as you put a current down a wire the
| magnetic field expands aways from a wire causing an apparent Lorentz
| force at a distance. After all, we know that as we put current down a
| wire energy is stored in the magnetic field. Causality means that
| energy is traveling away from the wire at the speed of light or
| slower. Therefore, the "expanding field" theory could make sense. But
| I've never found a calculation that would work to prove this. You try
| and nothing ends up making sense.
I'm not currently interested in trying to combine Lorentz and Faraday laws.
My interest right now is playing around with the Lorentz law and seeing
just what its boundaries are, especially with respect to the relativity
of motion. In other words, how far can I go with this concept of having
the magnets attached to the disk, and then modify the configuration beyond
the solid disk.
| Also as for Faraday Disks including the One Piece Faraday Homopolar
| Device (OPFHD) which means magnets rotate with disk. You CAN split the
| disk into radials or as Tesla proposed into a spiral which actually
| enhances the magnetic field as it produces current. It works the same.
That's an interesting one I had not seen. I looked at one patent Tesla
got that involved two disks edge to edge connected by some kind of belt
to make it easier to extract power. Back to Google.
| Yes then in the case of non-rotating magnets one actually can then say
| that the wires DO "cut" the flux. But in the one piece case, the
| problem is that you are using a loop to measure emf. One scenario is
| this: The magnet and the disk turn together. Therefore, there is NO
| emf induced into the disk no matter WHAT it's configuration! There is
| NO relative motion between them. The emf you are measuring is coming
| ALL from the wire loops hooked between the disk and meter. A similar
| argument ensues if you assume the magnetic field does not rotate with
| the magnet.
Are you saying this in terms of an argument one may face and have to ponder
or are you saying that the OPFHD really produces no EMF at all?
There is the counter argument that if the magnets rotate, and the disk
does not (wires are attached to measure), then this should induce some
voltage in the attached wires as well. Yet this configuration nets no
EMF.
But then, there is the counter argument to the counter argument that with
the magnets rotating, the disk is relatively going backwards with respect
to the magnets, and has an EMF in opposite polarity (compared to the disk
rotating and the magnets not) and this EMF bucks the EMF in the sensing
wires, resulting in nothing measured.
So which is it?
If the OPFHD really produces no EMF at all, then there was no paradox?
| These kind of experiments are easy to do. I've done quite a few. Just
| find some old dead large loudspeakers and remove the large ceramic
| disk magnets from them (they are usually glued in so it can take some
| work). Then set up your ideas. The voltages and currents from a
| Faraday disk should easily light most LEDs. But dig. They DON'T! All
| your various ideas somehow almost always seem to forget about the
| "complete" loop thing. The laws of line integrals in a conservative
| magnetic field are totally unforgiving! Nope, the LEDs do NOT light!
| Just gets you scratching your head. Evenually I had to join everyone
| else in the idea that the measurement cannot be made with a loop. It
| has to be made electrostatically. I don't like it, but it's just how
| it is.
I plan to buy some strong neodymium magnets to try things with when I do pick
an experiment to try.
I don't know what you mean by "measurement cannot be made with a loop". I am
not suggesting some kind of loop coupling to sense the EMF in the disk/wheel.
The loop is to generate a larger EMF potential. Putting the light on the
wheel itself is a means to directly measure without using brushes on the
disk.
I'm also considering the drum configuration. The conductors would run along
the drum parallel to the axis. The field would be radial to/from the axis.
And of course the motion would be circular around the drum.
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
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| Autymn D. C.... |
| Posted: Sun Jul 13, 2008 1:39 pm |
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Guest
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On Jul 12, 10:13 pm, Benj <bjac... at (no spam) iwaynet.net> wrote:
Quote: Are you saying this in terms of an argument one may face and have to ponder
or are you saying that the OPFHD really produces no EMF at all?
The OPFHG actually produces voltage (which seems rather amazing at
first) But if you use Lorentz arguments you have to say that since
there is no relative motion between the magnet and disk there can be
no Lorentz voltage. Thus EITHER the field rotates with the magnet and
Do you know the meaning of "piecewise"? |
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| ... |
| Posted: Sun Jul 13, 2008 3:24 pm |
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Guest
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On Sat, 12 Jul 2008 22:13:01 -0700 (PDT) Benj <bjacoby at (no spam) iwaynet.net> wrote:
| Yes, the dual Faraday generator used flanged disks with a copper mesh
| belt around them. This places (if you choose magnetic polarity
| correctly) the two generators in series which doubles the voltage (I
| think Tesla had the idea of a series of these to get voltages to
| useful ranges) and also lets the brushes be on the disk shafts rather
| than sliding on the disks (which has lots of friction and losses at
| the low voltages and high currents).
The original I idea I had was to have 2 parallel disks. Each disk would
have a magnet (same size as the disk) on each side. Looking down the axis
one disk would have both of its magnets with N-pole facing at you. The
other would have S-pole facing at you. These 2 disks would be spaced a
bit apart due to the S-poles facing each other. There would be field
lines reaching around each disk as well as going through each disk. Wires
would cross connect the two disks at their edges. The axis between disks
would be non-conductive.
This design is flawed because both disks would have the "extraneous" field
intersecting the cross-connect wires.
| The spiral one was interesting too in that he was trying build a "self-
| excited" Faraday generator. The idea was that the high currents in the
| spiral rotor automatically generate a stator field without a field
| supply or permanent magnets.
I'd have to see the geometry of this to know where the field lines would
be causing problems for this.
| The OPFHG actually produces voltage (which seems rather amazing at
| first) But if you use Lorentz arguments you have to say that since
| there is no relative motion between the magnet and disk there can be
| no Lorentz voltage. Thus EITHER the field rotates with the magnet and
| ALL the output voltage comes from the non-disk part of the circuit OR
| the field does NOT rotate with magnet in which case the voltage comes
| from the disk [no relative motion then between magnetic field and
| external wiring].
One or the other it seems.
|> There is the counter argument that if the magnets rotate, and the disk
|> does not (wires are attached to measure), then this should induce some
|> voltage in the attached wires as well. ?Yet this configuration nets no
|> EMF.
|
| The actual counter argument actually involves the case with the disk
| stationary and the brushes and meter are moving around the disk. And
| that DOES produce a voltage.
Another thing I have been wondering about is treating the Earth as a
OPFHG. While there are not conductors as we think of them extending
outward from the Earth, there actually are some, as well as a stream
of particles. So I wonder how much of this is charge from the Earth
rotating in its own magnetic field. There are some strange things like
"lightning sprites" emerging from the tops of storm clouds, suggesting
electrical fields extending much higher.
|> If the OPFHD really produces no EMF at all, then there was no paradox?
|
| But is does produce voltage. In fact the SAME voltage as if the
| magnets didn't move.
But is it really the OPFHD producing the voltage? Or is it there is
a voltage in the whole system consisting of the OPFHD and the wires
that are stationary, attached to brushes to extract current?
If those wires were constructed in a way that they were very loose
so that small forces could move them some distance to one side or the
other, would the rotation of the OPFHD mechanically deflect the wires?
If the voltage is being induced on these wires, shouldn't there be at
least some mechanical force, as well?
Of course one problem with this is, since these wires are carrying
current, and there is a magnetic field (we claim is stationary even
if the magnets are rotating), then I'd expect the wires to deflect
even if they are not where the EMF is induced. They would have their
own magnetic field, and that would interact with the rotor field.
|> I plan to buy some strong neodymium magnets to try things with when I do pick
|> an experiment to try.
|
| Me too! But right now I"m using Speaker magnets. One experiment is to
| encase the whole thing in an iron magnetic circuit (as Tesla did)
| Iron elements complicate the picture but I'm wondering what the effect
| of such flux concentration would be on output voltage and current.
| Especially if you spin the disk, magnets AND iron circuit! The thing
| I'm building needs a bit more machining before I try it.
|
|> I don't know what you mean by "measurement cannot be made with a loop". ?I am
|> not suggesting some kind of loop coupling to sense the EMF in the disk/wheel.
|
| It means that if you are measuring output using a meter and a
| "circuit" there is a loop of wire there and you MUST consider the
| ENTIRE loop for Lorentz forces. Consider the following: A spinning
| magnet. a "Loop" consisting of a wire down the axis of the disk shaft.
| A wire vertically up the face of the magnet. A wire away from the
| magnet following a "line of flux" and finally a vertical wire back
| down to the shaft where it is twisted with the other wire and goes to
| the meter. The standard thought is that if you make the flux line
| wires long enough, the downward wire will be in such a weak field that
| you can ignore any induction there. That is totally wrong!
There is an "extraneous" field going around a magnet between poles.
There is a field inside the magnet between them as well.
If you have 2 flat magnets, with poles on their flat faces, and they are
placed with the N-pole face of one close to the S-pole face of another,
you have a strong field between them. But there is also that "extraneous"
field going around the outward face of one to the outward face of the
other. Both of these fields have to be the same strength in much the
same ways as an electric circuit has the same current at two points.
| Dig. The wire down the shaft follows a fluxline and has no induction.
| The upper wire following a flux line has no induction. The twisted
| wire pair has no induced voltages. The wire up the magnet face will
| have the Lorentz force you expect due to the relative motion of the
| magnetic field and the wire. So far the experiment has everyone fat
| and happy. But wait. If you look closely, you'll find that the SAME
| flux lines that cut the wire on the magnet face ALSO cut the DOWNWARD
| connecting wire and do it in the OPPOSITE sense. You can show the
| induced voltages are equal and opposite! Hence you can experiment
| until you are blue in the face and you get NOTHING! And that also
| includes no conclusions! So long as there is a loop in the field you
| simply can't get around this cancellation! It turns out the loop shape
| makes no difference. This is why people suggest using electrostatic
| measurements which do NOT use a closed circuit to measure emf.
This is why I want to explore a modification of the field.
Consider a disk with 12 radials (so clock hour positions are easy ways
to identify specific radials).
The magnets I would use are half-donut shaped, with poles at the ends,
somewhat like a stubby horse-shoe magnet. These would be placed so that
the N-pole faces the disk from the top at radial 1, and S-pole faces the
disk from the top at radial 2, of the same magnet. Below the disk is
another magnet with its S-pole facing radial 1, and N-pole facing radial 2.
Several of these "facing pairs" would be placed along the radial, from 3/4
of the way away from the axis to the edge (so this is all in the outermost
1/4 of the disk, measured radially). Repeat for radials 3 and 4. Again
for 5 and 6. Then 7 and 8. Then 9 and 10. Then 11 and 12.
The conductor runs outward along radial 1, then jumps over to radial 2 at
the edge, then runs inward along radial 2, then jumps over to radial 3 at
the 3/4 distance. It repeats this back and forth until it reaches back
to radial 1 where it began. This is where we can insert the small light.
The disk itself is not a conductor. It would be a plastic frame holding
the conductor and the magnets.
The fields of these magnets are closely confined. The space between the
magnets above and below is kept close relative to the space between the
radials.
The orientation of the conductor is reversed where the magnetic field is
reversed. So any induced EMF should add up in each radial.
There are no "off the disk" stationary conductors (yet). If this does
induce EMF in the parts of the conductor directly between the magnets,
and if this EMF is going to be "bucked to zero" by other parts of the
conductor not directly between the magnets, then it will have to be in
the part where the conductor runs in the direction of disk rotation
between the radials. Even if there is magnetic field there, it's not
changing (since it is all rotating as one piece) so changing flux will
not be an influence. And the conductor direction is the same as the
motion direction, so that leaves insufficient conditions for any field
to induce an EMF by Lorentz law.
This configuration could also be done on a drum by having the radials
run parallel to the axis, with half the magnets outside and half inside
of the tubular surface of the drum.
|> The loop is to generate a larger EMF potential. ?Putting the light on the
|> wheel itself is a means to directly measure without using brushes on the
|> disk.
|
| Tried it. But if you think about it, you see that wires going to the
| light are the part of the light-loop! No light is seen.
So how can the configuration I describe above have this issue, where there
is enough "extraneous" induced EMF to fully buck the expected inducted EMF?
I hope my description of the configuration is clear enough. I'm very bad
at drawing, and even worse at 2D drawing of 3D depictions. I can imagine
my own ideas in 3D rather readily. I suppose what I need to do is learn
to use the POVRAY program to make my 3D ideas at least show up visually.
|> I'm also considering the drum configuration. ?The conductors would run along
|> the drum parallel to the axis. ?The field would be radial to/from the axis.
|> And of course the motion would be circular around the drum.
|
| Yes the drum configuration is good, See the old EM books by E.G.
| Cullwick who derives a lot on the drum and notes the "meter and
| brushes" relative motion thing.
I want to avoid the brushes as much as I can, at least until I can raise the
voltage and lower the current enough to make it not so much of an issue. In
the big design I gave above, if it really does induce an EMF, then I guess I
could take off power by having one end connected to one axis, and the other
end connected to the other axis (the axis in the middle being non-conductive).
| Good luck!
|
| WARNING: Due to extreme spam, googlegroups.com is blocked.
|
| Hey, I'm posting in GoogleGroups.com! How am I getting through? Is
| this evidence of superluminal transmission?
It seems you get through because you did followup on either a non-blocked post
or maybe my post, or a thread I posted in.
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
|
|
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|
| Benj... |
| Posted: Sun Jul 13, 2008 8:49 pm |
|
|
|
Guest
|
On Jul 13, 7:39 pm, "Autymn D. C." <lysde... at (no spam) sbcglobal.net> wrote:
Quote: On Jul 12, 10:13 pm, Benj <bjac... at (no spam) iwaynet.net> wrote:
Are you saying this in terms of an argument one may face and have to ponder
or are you saying that the OPFHD really produces no EMF at all?
The OPFHG actually produces voltage (which seems rather amazing at
first) But if you use Lorentz arguments you have to say that since
there is no relative motion between the magnet and disk there can be
no Lorentz voltage. Thus EITHER the field rotates with the magnet and
Do you know the meaning of "piecewise"?
Sure. As in "The dissipated rake had visited so many brothels in his
lifetime that he was very piecewise!" |
|
|
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|
| blackhead... |
| Posted: Mon Jul 14, 2008 8:16 am |
|
|
|
Guest
|
On 12 Jul, 12:19, phil-news-nos... at (no spam) ipal.net wrote:
Quote: It seems there is an error in this Wikipedia article:
http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction
Faraday's law says the induced EMF is in proportion to the rate of CHANGE
(my emphasis) of the magnetic flux. The article describes this much OK..
Later on, the article then says:
In the case of motional EMF, the idea is to move all or part of the
circuit through the magnetic field, for example, as in a homopolar
generator.
But this last case is a situation where the magnetic flux does not change..
Isn't this the aspect that Faraday saw as a paradox because it did not obey
his law of induction? Apparently he realized that no flux change happened
when he rotated the magnets with the rotating disk in his unipolar generator.
As I understand all this, there are TWO ways to induce electricity from a
magnetic field:
1. A conductor at a right angle to the magnetic field alignment experiencing
a change in the magnetic field flux density (strength). [Faraday's law
of induction]
2. Motion of a conductor at right angle to the magnetic field alignment and
simultaneously at right angle to the line of the conductor. [Fleming's
right hand rule, Lorentz force law]
Quote: The article seems to be trying to convert everything into one.
Which is correct, as far as Faraday's Law is concerned. The induced
EMF around a closed circuit is equal to the rate of change of flux
through the circuit and independent of whether it's the conductor or
the magnetic filed which is "moving".
Quote: |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
|
|
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|
| Szczepan Bia³ek... |
| Posted: Mon Jul 14, 2008 9:42 am |
|
|
|
Guest
|
<phil-news-nospam at (no spam) ipal.net> wrote news:g5do9h01noi at (no spam) news4.newsguy.com...
Quote:
Another thing I have been wondering about is treating the Earth as a
OPFHG. While there are not conductors as we think of them extending
outward from the Earth, there actually are some, as well as a stream
of particles. So I wonder how much of this is charge from the Earth
rotating in its own magnetic field. There are some strange things like
"lightning sprites" emerging from the tops of storm clouds, suggesting
electrical fields extending much higher.
Storm clouds are high voltage generators (Armstrong and Kelvin). As such
they must send electrons in ALL directions.
S*
> |
|
|
| Back to top |
|
| ... |
| Posted: Mon Jul 14, 2008 10:53 am |
|
|
|
Guest
|
On Mon, 14 Jul 2008 16:42:08 +0200 "Szczepan Bia?ek" <sz.bialek at (no spam) wp.pl> wrote:
|
| <phil-news-nospam at (no spam) ipal.net> wrote news:g5do9h01noi at (no spam) news4.newsguy.com...
|>
|> Another thing I have been wondering about is treating the Earth as a
|> OPFHG. While there are not conductors as we think of them extending
|> outward from the Earth, there actually are some, as well as a stream
|> of particles. So I wonder how much of this is charge from the Earth
|> rotating in its own magnetic field. There are some strange things like
|> "lightning sprites" emerging from the tops of storm clouds, suggesting
|> electrical fields extending much higher.
|
| Storm clouds are high voltage generators (Armstrong and Kelvin). As such
| they must send electrons in ALL directions.
How can a storm cloud generator a charge if it would send electrons in all
directions? Do these new charges emerge from some kind of singularity in
the middle of the cloud?
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
|
|
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|
| Don Kelly... |
| Posted: Mon Jul 14, 2008 10:53 pm |
|
|
|
Guest
|
<phil-news-nospam at (no spam) ipal.net> wrote in message
news:g5a3vt013mm at (no spam) news3.newsguy.com...
Quote: It seems there is an error in this Wikipedia article:
http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction
Faraday's law says the induced EMF is in proportion to the rate of CHANGE
(my emphasis) of the magnetic flux. The article describes this much OK.
Later on, the article then says:
In the case of motional EMF, the idea is to move all or part of the
circuit through the magnetic field, for example, as in a homopolar
generator.
But this last case is a situation where the magnetic flux does not change.
Isn't this the aspect that Faraday saw as a paradox because it did not
obey
his law of induction? Apparently he realized that no flux change happened
when he rotated the magnets with the rotating disk in his unipolar
generator.
As I understand all this, there are TWO ways to induce electricity from a
magnetic field:
1. A conductor at a right angle to the magnetic field alignment
experiencing
a change in the magnetic field flux density (strength). [Faraday's law
of induction]
2. Motion of a conductor at right angle to the magnetic field alignment
and
simultaneously at right angle to the line of the conductor. [Fleming's
right hand rule, Lorentz force law]
The article seems to be trying to convert everything into one.
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to
ignorance |
| by the abuse department, bellsouth.net is blocked. If you post
to |
| Usenet from these places, find another Usenet provider ASAP.
|
| Phil Howard KA9WGN (email for humans: first name in lower case at
ipal.net) |
---------------------------
Faraday considers the flux through a closed loop. Lorentz is a force
relationship considering, in this case, the force on an electron in a
conductor and the basic definition of potential difference.
Both situations occur in a normal motor- speed voltage due to motion and
"transformer "voltage due to the field. d(flux)/dt The flux through a path
may be a function of both time and position so it becomes d(phi with
position held constant)/dt + d(phi with time held constant )/dx times dx/dt
This accounts for both the magnetic field itself varying with time but also
the geometry varying with position which is changing with time. This appears
to be where the Wiki author is coming from-No problem.
If you look at a machines text such as Krause, you will see the two
terms -often expressed in terms of flux linkages or inductances d((Li)/dt
=L(di/dt) +i (dL/dt). In a motor the speed term generally is much larger
than the transformer voltage.
P.S. right angle motion is not required but that gives the most bang for the
buck -function of the sine of the angle. --
Don Kelly dhky at (no spam) shawcross.ca
remove the X to answer
------------------------------- |
|
|
| Back to top |
|
| ... |
| Posted: Tue Jul 15, 2008 1:55 am |
|
|
|
Guest
|
On Mon, 14 Jul 2008 11:16:39 -0700 (PDT) blackhead <larryharson at (no spam) softhome.net> wrote:
| On 12 Jul, 12:19, phil-news-nos... at (no spam) ipal.net wrote:
|> It seems there is an error in this Wikipedia article:
|>
|> ? ?http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction
|>
|> Faraday's law says the induced EMF is in proportion to the rate of CHANGE
|> (my emphasis) of the magnetic flux. ?The article describes this much OK.
|> Later on, the article then says:
|>
|> ? ? In the case of motional EMF, the idea is to move all or part of the
|> ? ? circuit through the magnetic field, for example, as in a homopolar
|> ? ? generator.
|>
|> But this last case is a situation where the magnetic flux does not change.
|> Isn't this the aspect that Faraday saw as a paradox because it did not obey
|> his law of induction? ?Apparently he realized that no flux change happened
|> when he rotated the magnets with the rotating disk in his unipolar generator.
|>
|> As I understand all this, there are TWO ways to induce electricity from a
|> magnetic field:
|>
|> 1. ?A conductor at a right angle to the magnetic field alignment experiencing
|> ? ? a change in the magnetic field flux density (strength). ?[Faraday's law
|> ? ? of induction]
|>
|> 2. ?Motion of a conductor at right angle to the magnetic field alignment and
|> ? ? simultaneously at right angle to the line of the conductor. ?[Fleming's
|> ? ? right hand rule, Lorentz force law]
|
|
|> The article seems to be trying to convert everything into one.
|
| Which is correct, as far as Faraday's Law is concerned. The induced
| EMF around a closed circuit is equal to the rate of change of flux
| through the circuit and independent of whether it's the conductor or
| the magnetic filed which is "moving".
But the Lorentz law is not about change of flux.
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
|
|
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|
| blackhead... |
| Posted: Tue Jul 15, 2008 3:05 am |
|
|
|
Guest
|
On 15 Jul, 07:55, phil-news-nos... at (no spam) ipal.net wrote:
Quote: On Mon, 14 Jul 2008 11:16:39 -0700 (PDT) blackhead <larryhar... at (no spam) softhome.net> wrote:
| On 12 Jul, 12:19, phil-news-nos... at (no spam) ipal.net wrote:
|> It seems there is an error in this Wikipedia article:
|
|> ? ?http://en.wikipedia.org/wiki/Faraday%27s_law_of_induction
|
|> Faraday's law says the induced EMF is in proportion to the rate of CHANGE
|> (my emphasis) of the magnetic flux. ?The article describes this much OK.
|> Later on, the article then says:
|
|> ? ? In the case of motional EMF, the idea is to move all or part of the
|> ? ? circuit through the magnetic field, for example, as in a homopolar
|> ? ? generator.
|
|> But this last case is a situation where the magnetic flux does not change.
|> Isn't this the aspect that Faraday saw as a paradox because it did not obey
|> his law of induction? ?Apparently he realized that no flux change happened
|> when he rotated the magnets with the rotating disk in his unipolar generator.
|
|> As I understand all this, there are TWO ways to induce electricity from a
|> magnetic field:
|
|> 1. ?A conductor at a right angle to the magnetic field alignment experiencing
|> ? ? a change in the magnetic field flux density (strength). ?[Faraday's law
|> ? ? of induction]
|
|> 2. ?Motion of a conductor at right angle to the magnetic field alignment and
|> ? ? simultaneously at right angle to the line of the conductor. ?[Fleming's
|> ? ? right hand rule, Lorentz force law]
|
|
|> The article seems to be trying to convert everything into one.
|
| Which is correct, as far as Faraday's Law is concerned. The induced
| EMF around a closed circuit is equal to the rate of change of flux
| through the circuit and independent of whether it's the conductor or
| the magnetic filed which is "moving".
But the Lorentz law is not about change of flux.
The Lorentz force is the solution to the differential form of
Faraday's Law, Curl E = -dB/dt.
Look at the abstract of this paper for example:
-------
<http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?
tp=&arnumber=995632&isnumber=21481>
Deriving the Lorentz force equation from Maxwell's equations
Abstract
A derivation of the Lorentz force equation is presented here based on
one of Maxwell'sequations, Faraday's law. The presentation is intended
to be understandable by those who have not recently studied
electromagnetism
-------
Blackhead
Quote: --
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
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